Efforts for improving the efficiency of design and manufacturing by utilizing 3D (three-dimensional) model data formed during a design process in CAE and CAM are widely practiced. However, 3D data may include small geometrical shapes of parts such as very small holes and grooves. In such cases, for example, a mesh that is used in CAE becomes very fine and the time of computation for analysis will increase.
For this reason, simplification to remove the shapes of some parts considered as having no effect on a solution of analysis calculation from a model is performed widely. Especially, in CAM, it is required to form an intermediate shape before machining from a final product shape as input data to machining equipment. The intermediate shape is formed by removing the shapes of some parts such as screw holes from the final product shape. In CAM, it is desirable that specified shapes and similar partial shapes can be removed collectively, because shapes that can be machined by each individual machining equipment are generally fixed.
As for geometry simplification, apparatus, and a similar shape search method, it is known that a shape is selected for simplification, based on parameters representing the dimensions of feature shapes, which is described, for example, in Japanese laid-open Patent publication No. 2000-331194. Also, in Japanese laid-open Patent publication No. 2001-117907, it is described that, for a polyhedral geometric model (polygon model), a polyhedral model is numerically represented from an axial moment function of a polyhedron and a similar model is searched out.
The above-mentioned techniques of prior art enable simplification of basic feature shapes such as holes and fillets in a batch fashion, based on their parameters. However, feature shapes that can be simplified are limited to those registered beforehand. Complex and large shapes are hard to simplify in view of efficiency, computation time, etc. The method of searching for a polyhedral shape similar to an arbitrary polyhedral shape is not capable of searching for a partial feature shape existing in a polyhedral shape and cannot accommodate needs sufficiently.
An object of the present invention is to allow for efficient selection of partial shapes similar to any specified portion in a model with regard to 3D geometric model data, thereby making it possible to efficiently perform geometry simplification even for complex and large shapes.